The long-term objective of this research is to understand the process of gene regulation of energy transduction, particularly in tissues with high energy requirements such as heart, brain, and smooth muscle. The Creatine Kinase (CK) gene family has a central role in the process of energy transduction, and is composed of four separate genes which are highly regulated in a tissue-specific, adaptive, and developmental pattern. The function of these four genes is described by the Creatine Phosphate (CP) shuttle hypothesis, in which mitochondrial ATP is a substrate for mitochondrial creatine kinase (MtCK) which reversibly catalyzes the transfer of high energy phosphate to creatine. The CP shuttle requires coordinate regulation of the cytosolic and mitochondrial Cks, and emphasizes the key position that MtCK has in regulating oxidative phosphorylation. The focus of this proposal is the regulation of energy transduction in aging human tissues. The CK genes have been chosen for study because of the paucity of information regarding gene regulation of energy transduction and mitochondrial biogenesis in aging human tissues, especially brain, and because preliminary data suggest that coordinate expression of the CK genes, BCK and ubiquitous MtCK (uMtCK) may be regulated posttranscriptionally by their conserved 3'-untranslated regions (UTR). The specific aims will define the coordinate regulation of all four CK genes in aging human tissues, and test the hypothesis that the 3'- UTRs of the KD genes are conserved because they exert posttranscriptional control of expression. These specific aims are: 1) Determine CK expression and activity in human brain, heart, and small intestine using autopsy tissues from aged and young adults. 2) Identify and characterize proteins binding to the 3'-UTRs of the CK mRNAs using RNA gel mobility- shift assays and affinity purification of RNA-binding proteins. Defining the process of gene regulation of energy transduction will significantly advance our understanding of the importance of energy production in non-sarcomeric tissues in health, aging, and in disease, such as stroke or senility.